I. Field
The present invention relates generally to communication, and more specifically to techniques for performing system selection and acquisition by a wireless device.
II. Background
Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, and Frequency Division Multiple Access (FDMA) systems. A CDMA system may implement a radio access technology (RAT) such as cdma2000 or Wideband-CDMA (W-CDMA). cdma2000 covers the well-known IS-2000, IS-856, and IS-95 standards.
IS-2000 and IS-95 support both voice and data services and are commonly referred to as “1x-EV-DV”, or simply “1x”, where the DV stands for “data and voice”. A wireless device (e.g., a cellular phone) supporting 1x typically maintains a preferred roaming list (PRL). This PRL contains information to assist the wireless device perform system selection and acquisition on 1x systems, particularly when the wireless device is roaming. The PRL identifies “permitted” systems that the wireless device should use and (optionally) “forbidden” systems that the wireless device should not use. The PRL format for 1x systems is described in a document TIA/EIA/IS-683-A, entitled “Over-the-Air Service Provisioning of Mobile Stations in Spread Spectrum Standards,” June 1998, which is publicly available.
IS-856 supports packet data service and is commonly referred to as “1xEV-DO”, where the DO stands for “data optimized”. A wireless device supporting 1xEV-DO also maintains a PRL for system selection and acquisition on 1xEV-DO systems. The PRL format for 1xEV-DO is described in a document TIA/EIA/IS-683-C, entitled “Over-the-Air Service Provisioning of Mobile Stations in Spread Spectrum Standards,” Oct. 25, 2002, which is also publicly available. IS-683-C describes (1) a PRL format that is an updated version of the PRL format defined by IS-683-A and that may be used for 1x systems and (2) an extended PRL format that may be used for both 1x and 1xEV-DO systems.
The PRL format defined by IS-683-A is different from the extended PRL format defined by IS-683-C. The different PRL formats cause problems for both “legacy” wireless devices that support IS-683-A and “new” wireless devices that support IS-683-C. A legacy wireless device is not able to recognize the extended PRL format and would not be able to perform system selection and acquisition if presented with an extended PRL. The legacy wireless device would then experience loss of service due to incompatible PRL formats. A new wireless device can recognize and use a PRL in the IS-683-A format. However, since the IS-683-A PRL format does not support 1xEV-DO, the new wireless device would not be able to acquire and receive services from 1xEV-DO systems. The new wireless device would then experience service limitation and limited ability to upgrade service information due to the limitations of the IS-683-A PRL. Both of the problems described above are highly undesirable.
There is therefore a need in the art for techniques to support system selection and acquisition for both legacy and new wireless devices.